While some electrically assisted racks or columns may operate without CAN communication, my guess is that most - perhaps all in OEM vehicles - are designed to expect CAN. Even the electrically powered pump units of the electro-hydraulic power assisted steering used for a decade in common cars (such as my Mazda 3, which uses the system of a Ford Focus) typically need a CAN message to run. Aside from self-driving, or even driver-assistance features such as lane keeping, communication is used to adjust the assist level dependent on road speed, steering angle, and/or steering rate. If there is one that just runs with power applied that's great, but use of CAN is normal, not Tesla-specific or necessarily related to autonomous driving.
I noticed in a discussion in another forum that the 2014 Model S P85 uses a Bosch EJ32‑3200‑DB, and that earlier models used the EJ32‑3200 series as well. This appears to be Bosch's belt-drive model or "EPSapa" (they have three series of electric power racks plus one powered column). Various Range Rover models use exactly the same unit, so it's not a Tesla-specific thing; in fact, Range Rover enthusiasts might be a better source of information than Tesla owners, since Tesla strongly discourages owners from modifying or even maintaining their own cars. The control computer for this system is mounted right on the end of the assist motor, so bypassing any of that seems unlikely.
By the way, this unit as used by Tesla has had quality problems with the bolts that hold the motor into the rack, leading to a recall and a documented fix.
I would be interested in seeing this done as well. I have researched several other options for 12V Electric Power Assisted Steering (EPAS) to the conclusion that they are cost prohibitive. EPAS Performance has an electric rack and pinion with a starting price of $2100, whereas you can get a used Tesla unit for $300 - $500. The guy at EVCreate has done the same thing with the Tesla supplied iBooster electric power brakes which he says can operate in "failsafe" mode without any CAN input. Can the Tesla EPAS also operate without a CAN input? The only other resource I was able to find was Tinkla whose goal is full self driving using OpenPilot. If the Tesla EPAS requires CAN input, I am curious if using OpenPilot could at least pass the required information and speed to the EPAS unit in order to make it operate as intended.
This would actually be a really good upgrade for any vehicle that has outdated vacuum boost power brakes and hydraulic power steering. Has anyone on this forum experimented with a Tesla EPAS unit without CAN input?
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